Purification of a lectin in high yield from the Indian lablab beans on goat IGM sepharose and by immunoaffinity chromatography: Evidence for the presence of endogenous lectin receptors

Abstract

Seeds of the Dolichos lab lab var. typicus (Indian lablab beans) contain a glucose/mannose specific lectin that has been affinity purified on Sepharose-mannose columns (1). We report here on the affinity purification of this lectin in high yields using alternate methods i) goat IgM Sepharose., and ii) Immuno-affinity chromatography (Lectin specific IgG coupled to Affi-gel-10). The molecular size and subunit pattern of the lectin purified by both methods was similar to that reported earlier. In addition the purified lectin could be quantitatively bound to Sepharose divinyl sulfone methyl α-mannopyranoside gel. Purified lectin was also found to be mitogenic to murine lymphocytes. Additionally Lectin-affinity chromatography (Lectin coupled to Affigel-10) indicated the presence of endogenous lectin receptors that specifically interact with the lectin without the involvement of the sugar binding site. Lectins are ubiquitous proteins/glycoproteins that are abundantly present in the legume seeds and have also been purified from some cereal seeds (2). Owing to their unique property of binding sugars in a reversible manner, lectins have found wide spread applications in different areas of modern biology (3). The genus Dolichos lablab contains two varities namely, var. lignosus (Field bean) and var. typicus (lablab bean). Both seeds contain glucose/mannose specific lectin that has earlier been affinity purified on Sepharose-mannose gel. Purified lectins exhibited similar physicochemical and biological properties (1). The objective of the present study was to develop alternate affinity methods for the purification of the lablab bean lectin in high yields and to study its fine sugar specificity as well as its other biological properties such as the mitogenecity and to identify endogenous lectin receptors from the seeds in order to understand the physiological significance of the lectin. The results obtained on these are presented here.